System and method for heating passenger cabin with inverter waste heat boosted by a heater

ABSTRACT

A vehicle includes an inverter, a climate control system, and a coolant system. The climate control system includes a housing, and a heater core and an electric heater disposed within the housing. The coolant system includes conduit arranged to circulate coolant through the inverter and the heater core. The inverter is disposed upstream of the heater core.

TECHNICAL FIELD

The present disclosure relates to hybrid-electric and fully electricvehicles that have a climate control system arranged to heat a passengercabin using heat generated by an inverter in combination with a heatbooster.

BACKGROUND

Traditional vehicles powered by an internal-combustion engine typicallyheat a passenger cabin of the vehicle using waste heat generated by theengine. Coolant heated by the engine is circulated to a heater coredisposed within a heating ventilation and air conditioning (HVAC) unit.The HVAC unit includes a blower that circulates an airstream through theheater core and into the passenger cabin to provide heat.

To improve fuel economy and diminish environmental impact, electric andhybrid electric vehicles have been developed to improve fuel economy andreduce pollution. These vehicles may generate none or insufficientengine waste heat to meet cabin-heating requirements. Consequently,other sources of heat are needed to sufficiently heat the cabin.

SUMMARY

According to one embodiment, a vehicle includes an inverter, an electricheater, and a heater core. A vehicle coolant system has conduit arrangedto circulate coolant through the inverter, the electric heater, and theheater core such that the electric heater is downstream of the inverterand upstream of the heater core.

According to another embodiment, a vehicle includes an inverter, aclimate control system, and a coolant system. The climate control systemincludes a housing, and a heater core and an electric heater disposedwithin the housing. The coolant system includes conduit arranged tocirculate coolant through the inverter and the heater core. The inverteris disposed upstream of the heater core.

According to yet another embodiment, a method of heating a passengercabin with a coolant system including an inverter, an electric heater,and a heater core is presented. The method includes operating aninverter to generate heat and circulating coolant through the inverterto transfer heat from the inverter to the coolant. The method furtherincludes boosting a temperature of the coolant with an electric heaterand circulating the coolant from the electric heater to the heater core.The method also includes heating an airstream bound for the passengercabin by circulating the airstream through the heater core.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a hybrid-electric vehicle.

FIG. 2 is a schematic diagram of a thermal management system having acoolant system and a refrigerant system that cooperate to heat apassenger cabin of the vehicle.

FIG. 3 is a schematic diagram of another thermal management systemhaving a coolant system and a refrigerant system that cooperate to heata passenger cabin of the vehicle.

FIG. 4 is a schematic diagram of a thermal management system having acoolant system and a heater for boosting a temperature of coolant withinthe coolant system.

FIG. 5 is a schematic diagram of a thermal management system having aheater disposed in a climate control system.

FIG. 6 is a schematic diagram of another thermal management systemhaving a heater disposed in a climate control system.

FIG. 7 is a flow chart illustrating an algorithm for controlling athermal management system having a refrigerant system that supplementswaste heat generated by at least an inverter.

FIG. 8 is a flow chart illustrating an algorithm for controlling athermal management system having an electric heater that supplementswaste heat generated by at least an inverter.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

FIG. 1 depicts a hybrid-electric vehicle (HEV) 12, but this disclosureis not limited to an HEV. The vehicle 12 may include one or moreelectric machines 14 mechanically coupled to a hybrid transmission 16.The electric machines 14 may be capable of operating as a motor or agenerator. In addition, the hybrid transmission 16 is mechanicallycoupled to an engine 18. The hybrid transmission 16 is mechanicallycoupled to a driveshaft 20 that is mechanically coupled to the wheels22. The electric machines 14 can provide propulsion and decelerationcapability when the engine 18 is turned ON or OFF. The electric machines14 also act as generators and can provide fuel economy benefits byrecovering energy that would normally be lost as heat in frictionbraking. The electric machines 14 may also reduce vehicle emissions byallowing the engine 18 to operate at more efficient speeds and allowingthe hybrid-electric vehicle 12 to be operated in electric mode with theengine 18 OFF under certain conditions.

A traction battery or battery pack 24 stores energy that can be used bythe electric machines 14. The vehicle battery 24 typically provides ahigh-voltage direct current (DC) output. The traction battery 24 iselectrically coupled to an inverter 26. One or more contactors 42 mayisolate the traction battery 24 from other components when opened andconnect the traction battery 24 to other components when closed. Theinverter 26 is also electrically coupled to the electric machines 14 andprovides the ability to bi-directionally transfer energy between thetraction battery 24 and the electric machines 14. For example, atraction battery 24 may provide a DC voltage while the electric machines14 may operate with three-phase alternating current (AC). The inverter26 may convert the DC to three-phase AC to operate the electric machines14. In a regenerative mode, the inverter acts as a rectifier to convertthe three-phase AC from the electric machines 14 acting as generators tothe DC compatible with the traction battery 24.

In addition to providing energy for propulsion, the traction battery 24may provide energy for other vehicle electrical systems. A vehicle 12may include a DC/DC converter module 28 that converts the high voltageDC output of the traction battery 24 to a low voltage DC supply that iscompatible with low-voltage vehicle loads. An output of the DC/DCconverter module 28 may be electrically coupled to an auxiliary battery30 (e.g., 12 volt battery). The low-voltage systems may be electricallycoupled to the auxiliary battery. Other high-voltage loads 46, such as acompressor, may be coupled to the high-voltage output of the tractionbattery 24.

One or more electrical loads 46 may be coupled to the high-voltage bus.The electrical loads 46 may have an associated controller that operatesand controls the electrical loads 46 when appropriate. Examples ofelectrical loads 46 may be a heating system or an air-conditioningsystem.

Electronic systems in the vehicle 12 may communicate via one or morevehicle networks. The vehicle network may include a plurality ofchannels for communication. One channel of the vehicle network may be aserial bus such as a Controller Area Network (CAN). One of the channelsof the vehicle network may include an Ethernet network defined byInstitute of Electrical and Electronics Engineers (IEEE) 802 family ofstandards. Additional channels of the vehicle network may includediscrete connections between modules and may include power signals fromthe auxiliary battery 30. Different signals may be transferred overdifferent channels of the vehicle network. For example, video signalsmay be transferred over a high-speed channel (e.g., Ethernet) whilecontrol signals may be transferred over CAN or discrete wires. Thevehicle network may include any hardware and software components thataid in transferring signals and data between modules. The vehiclenetwork is not shown in FIG. 1 but the vehicle network may connect toany electronic module that is present in the vehicle 12. A vehiclesystem controller (VSC) 48 may be present to coordinate the operation ofthe various components.

The inverter 26, the DC/DC converter 28, and other components generateheat during operation of the electric powertrain. This heat generationmay occur when the vehicle is utilizing the electric machines 14 topropel the vehicle and when the battery is being charged either throughregenerative braking or by a charge port if equipped. The heatgenerating components of the electric powertrain, such as the inverter26 and the DC/DC converter 28, may require one or more thermalmanagement systems to maintain the components within a desiredtemperature window. Typically, the waste heat generated by thecomponents is dissipated to the outside air and is not utilized forheating the cabin. This disclosure presents a plurality of climatecontrol systems arranged to utilize waste heat from the inverter 26 andthe DC/DC converter 28 to heat a passenger cabin of the vehicle 12.

Unlike an internal-combustion engine, which generates sufficient wasteheat to warm the cabin, the inverter 28 and the DC/DC converter 28 maynot produce enough waste heat to warm the cabin without the aid of aheat booster. The heat booster may increase the temperature of theworking fluid circulating through the heater core so that the cabin canbe fully heated, or may increase the temperature of an airstream withinthe heating ventilation and air conditioning (HVAC) unit.

FIGS. 2 through 6 disclose example embodiments of thermal managementsystems that heat the passenger cabin using waste heat of at least theinverter 26 in combination with a heat booster.

Referring to FIG. 2, a thermal management system 50 includes a coolantsystem 52, a refrigerant system 55 (heat booster), and a climate controlsystem 57. The coolant system 52 is configured to thermally regulate theinverter 26 and the DC/DC converter 28 and to provide waste heat to theclimate control system 57 by circulating coolant. Used herein, “coolant”refers to a liquid coolant such as ethylene glycol, other type ofanti-freeze, or other suitable liquid. The coolant system 52 may includea radiator 54, a pump 56, a valve 58, and conduit arranged to circulatethe coolant through the inverter 26, the DC/DC converter 28, theradiator 54, and other components of the system 50. The coolant system52 is also arranged to circulate coolant through a liquid-to-refrigerantheat exchanger (evaporator) 80 of the refrigerant system 55 to thermallyconnect the coolant system 52 and the refrigerant system 55.Liquid-to-refrigerant evaporators are sometimes called chillers.

The coolant system 52 may begin at the pump 56 which is connected to theDC/DC converter 28 by a first conduit 60. The DC/DC converter 28 isconnected to the inverter 26 by conduit 62. The valve 58 is locateddownstream of the inverter 26. The valve 58 may be a three-way valvethat includes an inlet 73 connected to the inverter 26 by conduit 64, afirst outlet 76 connected with conduit 66, and a second outlet 74connected to the radiator 54 by conduit 70. The conduit 66 conveyscoolant from the three-way valve 58 to the evaporator 80, and conduit 68returns to the pump 56. An exit side of the radiator 54 is connected tothe conduit 68 by conduit 72. The conduit 70 and 72 may be referred toas a radiator loop and the conduit 66 and 68 may be referred to as theevaporator loop.

The valve 58 may be electronically controlled and include a mechanismactuatable to proportion coolant between the outlets 74 and 76. Thevalve 58 may include a first position in which all of the coolant iscirculated to the outlet 76 and a second position in which all of thecoolant is circulated to the outlet 74. The valve 58 may further includeintermediate positions in which coolant flow is proportioned between theoutlets, e.g., the outlet 74 receives 30% of the coolant flow and theoutlet 76 receives 70% of the coolant flow. The valve 58 may include anactuator such as a motor that is in electronic communication with thecontroller 48 and operates according to instructions from the controller48. In an alternative embodiment, the three-way valve 58 may be replacedwith a pair of valves, which may be on-off valves as opposed to theabove-described proportioning valve. The pump 56 may also be inelectronic communication with the controller 48 and operate according toinstructions from the controller 48.

The refrigerant system 55, which may be referred to as a heat pump, maybe a vapor-compression system that circulates refrigerant between theevaporator 80 and a refrigerant-to-air heat exchanger (condenser) 82 tomove heat from evaporator 80 to the condenser 82. The condenser 82 maybe referred to as a heater core as it provides heat to the climatecontrol system 57. The refrigerant system 55 is powered by a compressor84 connected to the condenser 82 by conduit 88. The condenser 82 isconnected to the evaporator 80 by conduit 90. An expansion device 86 islocated on the conduit 90 upstream of the evaporator 80. The expansiondevice 86 may be an actuatable expansion device that has a series ofpositions including wide-open, closed, and throttled, or may be apassive expansion device such as an orifice tube. The expansion device86 lowers the temperature and pressure of the refrigerant prior toentering the evaporator 80. The evaporator 80 is connected to thecompressor 84 by conduit 92. The refrigerant system 55 may include otherknown components that will not be discussed, e.g., an accumulator.

The climate control system 57 is responsible for heating and/or coolinga passenger cabin 112 of the vehicle. The climate control system 57 mayinclude an HVAC unit 96 that is typically located under a dash of thevehicle. The HVAC unit 96 includes a housing 98 having an interior 100with one or more air passages or chambers 104 and 105 that are in fluidcommunication with each other. The air passage 104 includes a fresh-airinlet 102 that allows fresh air from outside the vehicle to be drawninto the HVAC unit 96. While not shown, the unit 96 may include arecirculated air vent that draws air from inside the cabin 112. An airduct 106 extends from the middle air passage 105 to at least one cabinvent 110 that releases a conditioned airstream into the passenger cabin112. The condenser 82 is disposed within the passage 105. A blower 108is arranged to circulate a fresh airstream through the condenser 82 toheat the fresh airstream prior to entering the cabin 112. While notillustrated, the HVAC unit 96 may include one or more valves, e.g.,blend doors, actuatable to control a temperature of the airstreamexiting the cabin vent 110 and to control air delivery to the at leastone air vents. An evaporator (not shown) of an air-conditioning systemmay be disposed within the housing 98 in some embodiments.Alternatively, the air-conditioning system may have a dedicated HVACunit. One or more temperature sensors (not shown) may be disposed withinthe HVAC unit 96 and in communication with the controller. Signals fromthe temperature sensor may be used to control the thermal managementsystem 50.

The thermal management system 50 may be operated in a plurality of modessuch as a cabin-heating mode and a cabin-off mode. During these modes,the inverter 26 and the DC/DC converter 28 may be cooled by the radiator54 (cabin-off mode), the evaporator 80 (cabin-heating mode), or acombination of both depending upon the embodiment.

According to one embodiment, the valve 58 is actuated to the firstposition when in the cabin-heating mode so that heat from the inverter26 and/or the DC/DC converter 28 are circulated to the evaporator 80rather than the radiator 54. The pump 56 is energized to circulate warmcoolant from the inverter 26 and the DC/DC converter 28 to theevaporator 80. The evaporator 80 transfers thermal energy from thecoolant to the refrigerant to cool the coolant for recirculation to theinverter 26 and the DC/DC converter 28 while simultaneously warming therefrigerant to provide heat into the refrigerant system 55. Thecompressor 84 is energized to circulate a highly compressed, hot vaporrefrigerant to the condenser 82. The blower 108 is energized to draw theoutside airstream through the condenser to heat the airstream deliveredto the cabin. Parameters of the refrigerant system, such as compressorpower and speed, and speed of the blower 108 can be varied to increaseor decrease the temperature of the airstream.

When in cabin-off mode, the valve 58 is actuated to the second positionto cool the DC/DC converter 28 and the inverter 26 with the radiator 54.When the valve 58 is in the second position, coolant is circulated tothe radiator loop to bypass the evaporator 80. The refrigerant system 55may not be utilized during cabin-off mode and may be deenergized.

Referring to FIG. 3, a thermal management system 120 includes a coolantsystem 122, a refrigerant system 124 (heat booster), and a climatecontrol system 126. The coolant system 122 is configured to thermallyregulate the inverter 26 and the DC/DC converter 28 and to provide wasteheat to the climate control system 126 by circulating coolant. Thecoolant system 122 may include a pump 128 and conduit 130 arranged tocirculate the coolant through the inverter 26, the DC/DC converter 28,and other components of the system 122. The coolant system 122 is alsoarranged to circulate coolant through a liquid-to-refrigerant heatexchanger (evaporator) 132 of the refrigerant system 124 to thermallyconnect the coolant system 122 and the refrigerant system 124.

The refrigerant system 124 circulates refrigerant between the evaporator132 and a refrigerant-to-air heat exchanger (condenser) 134 to move heatfrom evaporator 132 to the condenser 134. The refrigerant system 124 ispowered by a compressor 136 that circulates the refrigerant throughconduit 140 and the other components of the system 124. An expansiondevice 138 is located upstream of the evaporator 132.

The climate control system 126 is responsible for heating and/or coolingthe passenger cabin 112 of the vehicle 12. The climate control system126 may include an HVAC unit 142 that is typically located under a dashof the vehicle. The HVAC unit 142 includes a housing 144 having aninterior 146 with one or more chambers or passages that are in fluidcommunication with each other.

Unlike FIG. 2, the coolant system 122 does not include a radiator loopfor dissipating heat of the inverter 26 and the DC/DC converter 28.Instead, the inverter 26 and the DC/DC converter 28 are cooled byrejecting waste heat to the HVAC unit 142, i.e., by circulating anairstream through the condenser 134. The interior 146 may be split intoa first portion associated with transferring waste heat from theinverter 26 and the DC/DC converter 28, and a second portion associatedwith thermally regulating the cabin 112. The first and second portionsare selectively in fluid communication, and the first portion isupstream of the second portion. The first portion may include a firstchamber 148. The condenser 134 of the refrigerant system 124 may bedisposed within the first chamber 148. A first blower 154 is alsodisposed in the first chamber 148 upstream of the condenser 134 anddraws a fresh-air airstream through the first fresh air inlet 152 tocirculate the airstream through the condenser 134. The heated air may becirculated to an exterior vent 156, to the second portion, or acombination of both depending upon heating needs of the cabin 112.

The second portion may include a second chamber or passage 150 that isseparated from the first air chamber 148 by a dividing wall 162. An airpassageway or opening 166 extends through the dividing wall 162 toconnect the first chamber 148 and the second chamber 150 in fluidcommunication. A valve 164 opens and closes the passageway 166. In theillustrated embodiment, the valve 164 is a blend door that is pivotallyattached to the wall 162. When the blend door is in a first position(shown solid) the passageway 166 is completely blocked routing theairstream to the exterior vent 156. The first position corresponds to anon-heating mode of the cabin 112. When the blend door is in a secondposition (shown in phantom), the vent 156 is completely closed routingthe heated airstream into the second chamber 150 and subsequently intothe cabin 112 via at least one cabin vent 172.

The second chamber 150 may be in fluid communication with a second freshair inlet 158 so that the temperature of the airstream can becontrolled. A second valve 168, such as a blend door, controls the flowof fresh air into the chamber 150. When the valve 168 is in a firstposition (shown), fresh air is not drawn into the chamber 150 and fullyheated air is circulated to the cabin. The valve 168 may be opened to aseries of positions that introduce various amounts of fresh air toreduce the temperature of the airstream as desired.

A second blower 160 may be disposed in the chamber 150. The secondblower 160 may be used in conjunction with the first blower 154 to boostcirculation of air into the passenger cabin 112. The first and secondblowers 154, 160 may also be used independently of each other when thevalve 164 is closed to isolate the chamber 148 from the chamber 150.When the valve is closed, the blower 160 may circulate unheated air fromthe second fresh air inlet 158 into the cabin 112. In some embodiments,the evaporator 174 of the vehicle air-conditioning system may be housedin the second chamber 150. Here, the blower 160 circulates an airstreamthrough the evaporator 174 to condition the air for the passenger cabin112. In other embodiments, the vehicle air-conditioning system may havea dedicated HVAC unit, in which case the evaporator 174 is omitted fromthe unit 142.

At least one temperature sensor 171 may be disposed in the unit 142. Thesensor 171 is in communication with the controller 48. Signals from thetemperature sensor 171 may be used by the controller 48 to operate thecoolant system 122, the refrigerant system 124, and the climate controlsystem 126. For example, the controller 48 may utilize readings from thetemperature sensor 171 to control the compressor 136 and the blower 154to increase or decrease the temperature of the airstream as desired.

The thermal management system 120 may be operated in a plurality ofmodes such as a cabin-heating mode and a cabin-off mode. During both ofthese modes, the inverter 26 and the DC/DC converter 28 are cooled bythe evaporator 80. In cabin-off mode, the valve 164 is closed to isolatethe chamber 148 and the chamber 150 so that hot air is not circulatedinto the passenger cabin 112. The pump 128 and the compressor 136 areenergized so that waste heat from the inverter 26 and the DC/DCconverter 28 are rejected to the condenser 134. In this mode, thecompressor 136 is operated based on inverter 26 and DC/DC converter 28cooling needs. The blower 154 is energized to circulate an airstreamthrough the condenser and out of the exterior vent 156.

In cabin-heating mode, waste heat from the inverter 26 and the DC/DCconverter 28, which is boosted by the refrigerant system 124, istransferred to the airstream passing through the condenser 134. Thevalve 164 is at least partially open so that at least a portion of thehot airstream flows through the passageway 166 and into the secondchamber 150. The temperature of the airstream exiting the condenser 134may be reduced by actuating the valve 164, the valve 168, or both. Thetemperature of the airstream exiting the condenser 134 may be also bemodulated by controlling the compressor 136 albeit as a slave to coolingrequirements of the inverter 26 and the DC/DC converter.

FIG. 4 illustrates a thermal management system 180 that utilizes aheater for boosting the waste heat as opposed to a refrigerant system.The thermal management system 180 includes a coolant system 182 and aclimate control system 184. The coolant system 182 is configured tothermally regulate the inverter 26 and the DC/DC converter 28 and toprovide waste heat to the climate control system 182 by circulatingcoolant to a HVAC unit 186 of the climate control system 184. Thecoolant system 182 may include a radiator 188, a pump 190, a valve 192,a heater 194, and conduit 196 arranged to circulate the coolanttherethrough. The coolant system 122 is also arranged to circulatecoolant through a liquid-to-air heat exchanger (heater core) 204 that isdisposed in the HVAC unit 186. The coolant system 182 may begin at thepump 190 which is connected to the DC/DC converter 28 by a firstconduit. The DC/DC converter 28 is connected to the inverter 26 by asecond conduit. The valve 192 is located downstream of the inverter 26.The valve 192 may be a three-way valve that includes an inlet 198connected to the inverter 26, a first outlet 200 that is connected withthe heater 194, and a second outlet 202 that is connected to theradiator 188. The heater 194 is connected to the heater core 204, whichin turn is connected with the pump 190 to complete the fluid circuit.

The heater 194 may be an electric-resistance heater such as a positivetemperature coefficient (PTC) heater. The heater 194 may be powered bythe traction battery 24 or by a low-voltage auxiliary battery such as a12 or 24-volt (V) battery. Many electric vehicles utilize a PTC heateras the sole heat source for the passenger cabin. These PTC heaterstypically require high voltages and are powered by the high-voltage busas opposed to a low-voltage source, e.g., the 12 V auxiliary battery.The high-power PTC heaters typically require a large amount ofelectrical power, which reduces vehicle range. In this disclosure,however, the heater 194 is merely a booster for the inverter 26 andDC/DC converter 28. As such, a lower voltage heater may be utilized insome applications to extend the electric range. In others, the heater194 may be powered by the high-voltage bus. Other types of heaters mayalso be used.

The amount of heat boosting is dependent upon cabin-heating requirementsand the design of the heater core 204. In one embodiment, the heatercore 204 is designed to receive a 90 degrees Celsius coolant in order toprovide high heat. Depending on operating conditions, the inverter 26and the DC/DC converter 28 may only heat the coolant to 70 degreesCelsius, in which case, the heater 194 is operated to boost the coolanttemperate by 20 degrees Celsius. These temperatures are merelyillustrative and are not limiting. The coolant system 182 may include atemperature sensor 211 disposed downstream of the inverter 26 and DC/DCconverter 28 and upstream of the heater 194. The temperature sensor 211is configured to sense a temperature of the coolant circulatingtherethrough, and output a signal indicative of the coolant temperatureto the controller 48. The controller 48 may operate the heater 194 basedon signals from the temperature sensor 211.

The valve 192 may be electronically controlled and include a mechanismactuatable to proportion coolant between the outlets 200 and 202. Thevalve 192 may include a first position in which all the coolant iscirculated to the outlet 200 and a second position in which all thecoolant is circulated to the outlet 202. The valve 192 may furtherinclude intermediate positions in which coolant flow is proportionedbetween the outlets. The valve 192 may be in electronic communicationwith the controller 48 and operate according to instructions from thecontroller 48. In an alternative embodiment, the three-way valve 192 maybe replaced with a pair of valves, which may be on-off valves as opposedto the above-described proportioning valve.

The HVAC unit 186 may include a housing 206 defining an interior 208.The heater core 204 is disposed within the interior 208 and isconfigured to receive a fresh airstream from a fresh air inlet 210. Theblower 212 is disposed upstream of the heater core 204 and circulatesair through the HVAC unit 186. The HVAC unit 186 includes at least onecabin vent 218 that provides air into the passenger cabin 112. Anevaporator 207 of the vehicle air-conditioning system may be disposed inthe HVAC unit 186 upstream of the heater core 204 as is traditionallydone. Alternatively, the air-conditioning system may have a separatehousing. A valve 214, such as a blend door, controls air flow throughthe heater core 204 to control the temperature of the air exiting thecabin vent 218. The valve may be optional as the valve 192 and theheater 194 can be actuated to control the temperature of the heater core204.

Similar to operation of thermal management system 50, the controller 48may actuate the valve 192 between various positions depending upon anoperating mode of the thermal management system 180. The valve 192 maybe actuated to the first position when in the cabin-heating mode so thatthe heat from the inverter 26 and the DC/DC converter 28 are circulatedto the heater 194 and the heater core 204 rather than the radiator 188.The pump 190 is energized to circulate warm coolant from the inverter 26and the DC/DC converter 28 to the heater 194, which boosts the coolanttemperature prior to circulating to the heater core 204 if needed. Theheater core 204 transfers thermal energy from the coolant to theairstream to cool the coolant for recirculation to the inverter 26 andthe DC/DC converter 28 while simultaneously warming the airstream toprovide heat to the cabin 112. The blower 212 is energized to draw theoutside airstream through the heater core 204.

When in cabin-off mode, the valve 192 is actuated to the second positionto cool the DC/DC converter 28 and the inverter 26 with the radiator188. When the valve 192 is in the second position, coolant is circulatedto the radiator loop to bypass the heater core 204.

FIG. 5 illustrates another thermal management system 230 that is similarto the embodiment of FIG. 4 but heats the air with a heater 232 ratherthan heating the coolant. The thermal management system 230 includes acoolant system 234 that has a valve 236 configured to circulate coolantto the radiator 238 when the valve 236 is in a first position and tocirculate coolant to an HVAC unit 242 of the climate control system 234when in a second position. A heater core 246 is in fluid communicationwith the coolant system 234 is disposed within an interior of the HVACunit 242. The heater 232 is disposed downstream of the heater core 246to boost a temperature of the airstream after passing through the heatercore 246 if needed. The heater 232 may be electronically controlled bythe controller 48 and is energized by the controller 48 when the heatercore 246 is incapable of heating the airstream to a desired temperature.A temperature sensor 248 may be disposed within the HVAC unit 242downstream of the heater core 246 and upstream of the heater 232. Thetemperature sensor 248 is in electronic communication with thecontroller 48 and is configured to output a signal indicative of theairstream temperature exiting the heater core. The controller 48 mayoperate the heater 232 based on signals from the sensor 248. Forexample, if the airstream temperature is less than the desired airstreamtemperature as sensed by the sensor 248, the controller 48 may energizethe heater 232 to boost the temperature of the airstream to the desiredtemperature.

Referring to FIG. 6, a thermal management system 250 includes a coolantsystem 252, a heater 256 (heat booster), and a climate control system254. Similar to FIG. 3, the thermal management system 250 does notinclude a radiator for cooling the inverter 26 and the DC/DC converter28, and instead circulates the waste heat to the HVAC unit 264 of theclimate control system 254 to release the waste heat to the outside air,circulate the waste heat into the passenger cabin 112, or a combinationof both. The coolant system 252 includes a pump 258 and conduit 260arranged to circulate coolant through the DC/DC converter 28, theinverter 26, and a liquid-to-air heat exchanger (heater core) 262 thatis disposed within the HVAC unit 264.

The climate control system 254 is responsible for heating and/or coolingthe passenger cabin 112 and thermally regulating the inverter 26 andDC/DC converter 28. The HVAC unit 264 includes a blower 266 that drawsair from a fresh-air inlet 268 to circulate an airstream through theheater core 262 to transfer thermal energy from the coolant to theairstream. The speed of the blower 266 can be increased or decreaseddepending upon the cooling needs of the inverter 26 and the DC/DCconverter 28. The now-heated airstream may be circulated to an exteriorvent 274 when cabin heat is not requested or can be circulated to thecabin 112 when heat is requested. A valve 272, e.g., a blend door,controls the circulation of the airstream between the exterior vent 274and at least one cabin vent 278. A second blower 276 may be disposeddownstream of the valve 272 to supplement the first blower 266. Whilenot illustrated, one or more additional fresh-air/recirculation inletsmay be provided downstream of the valve 272. The air-conditioning systemof the vehicle may be integrated with the HVAC unit 264 or may have adedicated HVAC unit.

The heater 256 may be used to heat the air within the HVAC unit 264 (asshown) or may be integrated with the coolant system 252 to heat thecoolant (similar to FIG. 4). In the illustrated embodiment, the heater256 is disposed in the HVAC unit 264 downstream of the valve 272 and thesecond blower 276 (if present) to boost the temperature of the airstreamwhen needed. The heater 256 may be similar to the heater 232 describedabove. The heater 256 is in electronic communication with the controller48 and may be controlled to increase or decrease the temperature of theairstream circulating through the cabin vents 278 based on cabin heatingdemands. A temperature sensor 279 may be disposed between the heatercore 262 and the heater 256 to determine a temperature of the airstreamexiting the heater core 262. The controller is in communication with thesensor 279 and may control the heater 256 based on signals from thesensor 279. For example, if the desired air temperature is 26 degreesCelsius and the sensor 279 is reading 20 degrees Celsius, then thecontroller 48 may operate the heater 256 to boost the airstream by 6degrees Celsius.

Control logic or functions performed by controller 48 may be representedby flow charts or similar diagrams in one or more figures. These figuresprovide representative control strategies and/or logic that may beimplemented using one or more processing strategies such asevent-driven, interrupt-driven, multi-tasking, multi-threading, and thelike. As such, various steps or functions illustrated may be performedin the sequence illustrated, in parallel, or in some cases omitted.Although not always explicitly illustrated, one of ordinary skill in theart will recognize that one or more of the illustrated steps orfunctions may be repeatedly performed depending upon the particularprocessing strategy being used. Similarly, the order of processing isnot necessarily required to achieve the features and advantagesdescribed herein, but is provided for ease of illustration anddescription. The control logic may be implemented primarily in softwareexecuted by a microprocessor-based vehicle, engine, and/or powertraincontroller, such as controller 48. Of course, the control logic may beimplemented in software, hardware, or a combination of software andhardware in one or more controllers depending upon the particularapplication. When implemented in software, the control logic may beprovided in one or more computer-readable storage devices or mediahaving stored data representing code or instructions executed by acomputer to control the vehicle or its subsystems. The computer-readablestorage devices or media may include one or more of a number of knownphysical devices which utilize electric, magnetic, and/or opticalstorage to keep executable instructions and associated calibrationinformation, operating variables, and the like. Any reference to “acontroller” refers to one or more controllers.

FIG. 7 is a flowchart 300 of an algorithm for controlling a thermalmanagement system having a refrigerant system that supplements the wasteheat generated by the inverter and/or the DC/DC converter, such theembodiments of FIGS. 2 and 3.

At operation 301 at least the inverter is operated to generate wasteheat. At operation 302 the controller determines if cabin heating isrequested. If yes, control passes to operation 304 and coolant iscirculated through the evaporator. Depending upon the design of thethermal management system, coolant may be circulated through theevaporator but merely energizing the pump, e.g., FIG. 3, or byenergizing the pump and actuating at least one valve so that coolant isrouted to the evaporator, e.g., FIG. 2.

At operation 306, the refrigerant system is activated to circulaterefrigerant through the condenser. The refrigerant system may beactivated by energizing the compressor and actuating the expansiondevice(s) (if applicable). The controller may operate the compressorbased on cooling needs of the inverter and the DC/DC converter as wellas cabin heating needs.

At operation 308, the blower within the HVAC unit is turned ON tocirculate an airstream through the condenser. The climate control systemis operated to provide the desired heating to the cabin at operation310. This may include modulating the blower speed and/or operating oneor more blend doors within the HVAC unit.

If cabin heating is not being requested at operation 302, control passesoperation 312 and the thermal management system is operated to rejectwaste heat to the outside air. In FIG. 2 for example, the waste heat isrejected by a radiator. The controller may command one or more valves toroute the coolant to the radiator rather than the evaporator atoperation 312. In the illustrated embodiment of FIG. 3, the controllermay operate a blend door within the HVAC unit to route the airstream tothe external vent of the HVAC unit at operation 312.

FIG. 8 is a flowchart 350 of an algorithm for controlling a thermalmanagement system having an electric heater that supplements the wasteheat generated by the inverter and/or DC/DC converter, such as theembodiments of FIGS. 4, 5, and 6.

At operation 352 at least the inverter is operated to generate wasteheat. At operation 354 the controller determines if cabin heating isrequested. If yes, control passes to operation 356 and coolant iscirculated through the heater core. Depending upon the design of thethermal management system, coolant may be circulated through the heatercore by merely energizing the pump, e.g., FIG. 6, or by energizing thepump and actuating at least one valve so that coolant is routed to theheater, e.g., FIGS. 4 and 5. At operation 358, the blower within theHVAC unit is energized to circulate an airstream through the heatercore. At operation 360, the heater is activated if the waste heatgenerated by at least the inverter is insufficient to provide thedesired cabin heating. For example, in the embodiment of FIG. 4, thecontroller may monitor a temperature of the coolant exiting the inverterand if the coolant temperature is below a desired coolant temperature,the heater is activated to boost the temperature of the coolantcirculating to the heater core. In the embodiment of FIG. 5, forexample, the controller may monitor the temperature of the airstreamexiting the heater core, and if the airstream temperature is less thanthe desired temperature, activate the heater to heat the airstream priorto entering the passenger cabin.

At operation 362 the climate control system is operated to provide thedesired heating to the passenger cabin. For example, the controller maymodulate the blower speed and/or actuate one or more blend doors withinthe HVAC unit to provide the desired air temperature at the desiredcabin vents, e.g., floor, dash, defrost, etc.

If cabin heating is not being requested at operation 354, control passesoperation 364 and the thermal management system is operated to rejectwaste heat to the outside air. In FIG. 4 for example, the waste heat isrejected by a radiator. The controller may command one or more valves ofthe coolant system to route the coolant to the radiator rather than theheater core at operation 364. In the illustrated embodiment of FIG. 6,the controller may operate a blend door within the HVAC unit to routethe airstream to the external vent at operation 364.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes can be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments can becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics can becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes caninclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and can be desirable for particularapplications.

What is claimed is:
 1. A vehicle comprising: a heating ventilation andair conditioning (HVAC) unit including: a housing defining an air inlet,a cabin vent, and an exterior vent that vents air outside of thevehicle, a blend door disposed downstream the exterior vent and upstreamthe cabin vent, the blend door including a first position in which theair inlet and the cabin vent are in fluid communication and a secondposition in which the air inlet and the cabin vent are not in fluidcommunication, a heater core disposed within the housing between the airinlet and the blend door, and an electric heater disposed within thehousing downstream of the blend door; and a coolant system includingconduit arranged to circulate coolant through the inverter and theheater core.
 2. The vehicle of claim 1, wherein the HVAC unit furtherincludes a first blower disposed within the housing upstream of theheater core and a second blower disposed within the housing downstreamof the blend door.
 3. The vehicle of claim 1, wherein the coolant systemis valveless.
 4. The vehicle of claim 1 further comprising a controllerprogrammed to, in response to cabin heating not being requested, actuatethe blend door to the second position.
 5. The vehicle of claim 1 furthercomprising: a temperature sensor disposed within in housing downstreamof the heater core and upstream of the electric heater, the sensor beingconfigured to output a signal indicative of an air temperature; and acontroller programmed to: in response to cabin heating being requested,actuate the blend door to the first position, and in response to the airtemperature being below a desired temperature, energize the electricheater.